Autonomous robots are known in the art and have been implemented as household appliances, such as a lawnmower or a vacuum cleaner. These household appliances operate by moving about an area to be processed such that the entire area is covered by the end of the operation.
Reference is now made to FIGS. 1A and 1B which illustrate the operation of one exemplary autonomous robot, described in U.S. patent application Ser. No. 08/554,691, filed 7 Nov. 1995, and assigned to the common assignees of the present invention. U.S. patent application Ser. No. 08/554,691 is incorporated herein by reference. FIG. 1A illustrates the area in which the robot 10 operates and FIG. 1B illustrates the elements, in block diagram form, of robot 10.
The autonomous robot 10 operates within an area marked with boundary markers 12A. If there are fixed obstacles 14 in the area, such as flower beds, trees, columns, walls, etc., these obstacles are rimmed with further boundary markers 12B. The boundary markers 12 can be of any suitable type, such as an electrified wire, bar coded posts, radioactive posts, etc. The term “marker” will be used herein for both posts and wires.
As shown in FIG. 1B, the robot 10 includes a navigation system 20 which receives data from an edge sensor 22 which senses when the robot 10 approaches a boundary marker 12 where, if the marker is a continuous wire, the term “marker” indicates the section of the wire near the current location of the robot. The navigation system 20 also receives data from an odometer 24 which measures the distance the robot 10 has moved and a compass 26 which measures the current location of the robot 10.
Initially, the robot 10 is placed within the area to be covered. The robot 10 moves toward the boundary (if it did not begin near it) and then, as indicated by arrows 32, moves along the boundary, following the boundary markers 12. During this process, the robot 10 uses the location information from the compass to produce a map 28 (FIG. 1B) of the area to be covered.
Once the map is complete, the robot 10 moves about the area to be covered. Whenever it approaches a boundary marker 12, as sensed by the edge sensor 22, the robot 10 changes direction and continues until it reaches another boundary marker 12. If the boundary marker 12 appeared close to, but not at, its expected position, navigation system 20 updates the map 28 to match the new information.
If the boundary marker 12 is sensed substantially within the area, as determined by a comparison of the output of the compass 26 and the information in the map 28, the boundary marker 12 must be one which surrounds the obstacle 14. The robot 10 changes direction and continues until it reaches another boundary marker 12. The robot 10 moves about the area to be covered until it has determined that all sections of the map 28 have been covered.
However, it will be appreciated that creating the map 28 of the shape of the area to be covered is time consuming. Due to the inaccuracies of the compass 26 and odometer 24, it is also typically error prone.